1. Field of the Invention
The present invention relates to a metal mold, and more particularly to a metal mold with additional thermo chamber sprout for providing homogeneous and high temperature distribution over the mold thereby benefiting robust molding process of compact workpiece.
2. Description of the Prior Art
Conventionally, magnesium and aluminum are ideal metal for injection molding because their melting temperatures are lower than steel which is usually used for mold. In addition, both magnesium and aluminum have very good flow capacity, accordingly, it can be used for molding compact workpiece, such as an enclosure of notebook computer.
Referring to FIG. 8, a typical mold includes a male mold half (a), and a female mold half (b) and each is formed with a cavity (a1, b1), a plurality of distributing channels (a2, b2), and a sprout (c) in communication with the distributing channels (a2). The male mold half (a) is equipped with a plurality of heating tubes (d), as shown in FIGS. 9 and 10. The female mold half (b) further includes a recess (b3) in adjacent to the distributing channels (b2) for receiving the sprout (c) of the male mold half (a). The female mold half (b) further includes an inlet (b4) which receives molten metal through a nozzle (e1) of an ejector (e), thereby filling the cavities (a1, b1), as clearly shown in FIGS. 11 and 12.
Since the male and female mold halves (a, b) are used to form the compact workpiece, such as the notebook enclosure, the cavities (a1, b1) have a very thin thickness. In order to ensure the molten metal can completely fill the cavities (a1, b1) before it is consolidated resulted from temperature differential, the male mold half (a) should constantly heated by the heating tube (d).
In general, during the injection molding process of the molten metal, such as the Mgxe2x80x94Al alloy, the temperature of the male and female mold halves (a, b) should be kept around 350-370 degrees Celsius. However, as the heat loss of the heating tube (d) through its length, the temperature of the male mold half (a) can only be heated around 170 to 180 degrees Celsius. As a result, the filling of the molten metal within the cavities (a1, b1) will be heavily impaired. For example, the molten metal starts to consolidate right after it reaches to the cavities (a1, b1). It is unlikely that the molten metal can completely fill the cavities (a1, b1), especially to the detailed portions of the cavities (b1, a1). Consequently, the defective workpiece are increased and which results increasing of the cost.
It is a primary object of the present invention to provide a metal mold with additional thermo chamber sprout for providing homogeneous and high temperature distribution over the mold thereby benefiting robust molding process of compact workpiece.
A further object of the present invention is to provide a metal mold with a bottom mold half arranged between a male mold half and a holder of an injecting machine. Therefore, the holder 6 is prevented from being overheated by the male mold half.
In order to achieve the objective set forth, a mold with additional thermo chamber for homogenous temperature distribution in accordance with the present invention comprises a first mold half having a first mold cavity and a plurality of first distributing channels directing to the first mold cavity. The first mold half further includes a sprout in communicating with the first distributing channels. A second mold half has a second mold cavity corresponding to the first mold cavity. The second mold half further includes a recess for receiving the sprout of the first mold half. The second mold further includes an inlet in communicating with the sprout for receiving molten metal. A third mold half is assembled to the first mold half. A thermo chamber is defined between the third mold half and the first mold half for receiving molten metal therein thereby increasing mold temperature of the first mold.